This invention relates to laser micromachining apparatus.
Several methods of micromachining substrates have previously been proposed or utilized -- see "Review of Laser Microwelding and Micromachining" (K. G. Nichols) -- PROC IEE Vol. 116 No. 12 Dec. 1969. They fall into several groups, the first being mechanical methods using needles, ultrasonic drills, or a jet of fluid or small particles. Such mechanical methods have generally been found to be time-consuming and not capable of very fine and clean machining. Furthermore, they appear to be often limited to a particular class of materials.
Electrical methods utilizing electron beam or electrical spark apparatus have also been used. The electron beam has been found to be very fast and very accurate, but the technique has, in practice, proved to be very involved and expensive, the substrate having to be mounted in a vacuum and only one point being processed at a time. On the other hand, the electrical spark apparatus is not very involved and is not expensive but does appear to be very limited in its scope and not capable of wide use.
Chemical methods have been used and these are very accurate and not too expensive but they do require several operations and are time-consuming in practice. Electrodeposition methods require a conducting surface to start with whilst the depth of penetration which is obtainable by etching cannot generally exceed the width of the cut on the surface, due to the inherent V-shape of the cut. Moreover, it would appear that certain substrates, such as paper and rubber, cannot be etched properly.
A focussed laser beam has previously been used and has been found capable of working on a wide variety of materials. However, most existing systems operate on only one point at a time.
It is an object of the present invention to provide laser micromachining apparatus in which the above-mentioned disadvantages are substantially reduced or obviated and wherein the apparatus is capable of working on a relatively wide variety of substrates and on a large number of points simultaneously, whilst maintaining a high resolution and a high production rate where possible.